1. Field of the Invention
The embodiments of the invention generally relate to far back end of the line (FBEOL) structures and, more particularly, to FBEOL solder connector structure that incorporates a thin conformal conductive layer to optimize contact and adhesion between ball limiting metallurgy (BLM) layers and a conductive via.
2. Description of the Related Art
Aluminum has generally been removed from chip processing due to the replacement of aluminum with copper in the chip wiring levels. However, conventional far back end of the line (FBEOL) solder connectors are still being formed with a thick aluminum or aluminum alloy pad between the copper via and the ball limiting metallurgy (BLM) layers with which a solder ball connection (e.g., a controlled collapse chip connection (C4)) is made.
As addressed in U.S. patent application Ser. No. 11/308,359, filed on Apr. 4, 2006, and incorporated herein by reference, it would be advantageous over the prior art to remove this thick aluminum pad from the solder connector structure and, thus, to completely eliminate the use of aluminum in chip processing. Specifically, removing the aluminum pad from the connector structure would eliminate an entire process sequence associated with the aluminum level, including deposition, resist and lithography, and reactive ion etching, as well as eliminate the need for a chromium phosphate cleaning process, which presents environmental concerns. Other problems associated with aluminum, include, the fact that is has a low melting point and worse electro-migration characteristics when compared to other metals (e.g., copper). Additionally, elimination of the thick aluminum pad will allow for device scaling, process simplification and cost reductions.